A cDNA probe prepared from an AMV (MAV) RNA template was hybridized to a Southern blot of restriction fragments from cell line Q5 DNA. This line consists of quail cells that have been transformed by avian myelocytomatosis virus MC29 but do not produce virus. The probe hybridized predominantly to a single BamHI fragment and a single EcoRI fragment which suggests that the integrated provirus within Q5 is located at a single site that is stable through cell division. The probe used in this experiment was shown to be virus specific since it predominantly hybridized to restriction fragments in chicken DNA that have been found to contain endogenous virus-related sequences.